Ответ:

2 1

341+(431-134)= 638

1. 431-134= 297

2. 341+297= 638

2 1

434-(343-43)= 134

1. 343-43= 300

2. 434-300= 134

2 1

85+(577-236)= 426

1. 577-236= 341

2. 85+341= 426

2 1

222+(333-144)= 411

1. 333-144= 189

2. 222+189= 411

3 1 2

99+(890-800):3= 129

1. 890-800= 90

2. 90:3= 30

3. 99+30= 129

3 1 2

1000-(320-20):10 = 970

1. 320-20= 300

2. 300:10= 30

3. 1000-30= 970